JPH07119449A - Exhaust emission control device for engine - Google Patents

Abstract

PURPOSE:To increase the temperature of a catalyst in a short time and to improve exhaust gas purifying efficiency by a method wherein, when it is right after starting of an engine and an exhaust gas temperature is not sufficiently increased, exhaust gas is stored in a cylinder without being discharged in the air and a catalyst converter is introduced when occasion demands. CONSTITUTION:When, after starting of an engine 1, the warming-up state of the engine 1 and upper and lower catalyst converters 12 and 13 are respectively detected, a flow passage switch valve 15 and two oxygen density sensors 48 and 49 are respectively controlled by an electronic control device 38. For example, when a detecting temperature is below a set temperature, the opening direction of the flow passage switch valve 15 is switched such that exhaust gas flows from the downstream catalyst converter 13 to a route 16 and exhaust gas is introduced to a compressor 18. Simultaneously, the compressor 18 is driven with the aid of a motor 27 and exhaust gas introduced thereto is compressed to guide the compressed exhaust gas through a route 34 to a cylinder 29. Further, when a detecting temperature exceeds a set temperature, exhaust gas from the downstream catalyst converter 13 is caused to flow to the muffler 10 side, and exhaust gas in the cylinder 29 is caused to flow to a position situated upper stream from the downstream catalyst converter 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine exhaust gas purification apparatus applied to a vehicle engine such as an automobile.

[0002]

2. Description of the Related Art Since an engine mounted on a vehicle such as an automobile uses gasoline as a fuel, exhaust gas after combustion in a combustion chamber contains various harmful components. If these harmful components are released into the atmosphere as they are, the health of the residents near the road will be impaired, and it will be unfavorable from the viewpoint of environmental protection.Therefore, the exhaust gas between the engine combustion chamber and the tail pipe An exhaust purification device is usually provided in the system.

As this exhaust gas purification device, a catalytic converter is often used as disclosed in, for example, Japanese Utility Model Laid-Open No. 3-6012. The catalytic converter purifies harmful components in the exhaust gas. As the catalytic converter, an oxidation catalytic converter that processes hydrocarbons and carbon monoxide in an oxidizing atmosphere, a reducing catalytic converter that processes nitrogen oxides in a reducing atmosphere, and a three-way system that simultaneously processes the above three components at a stoichiometric air-fuel ratio There is a catalytic converter, but in any case it is necessary for the catalyst to be up to a certain temperature for it to function satisfactorily, otherwise the throughput will drop.

In order for the catalytic converter to exert its purification performance sufficiently, it is preferable to keep the temperature of the catalyst at 300 to 400 ° C. or higher. In addition, in order to prevent the performance deterioration of the catalyst, it is necessary to consider not to exceed a certain temperature. In order for the catalytic converter to exert its purification performance sufficiently, it is better to set it to the above temperature, but immediately after starting the engine that was stopped, the engine temperature is low and the exhaust temperature is also low. In such a case, good exhaust gas purification with a catalytic converter cannot be expected.

Therefore, after the engine is started, the vehicle is not made to run immediately but warmed up to wait for the lubricating oil of the engine to rotate and at the same time raise the temperature of the exhaust gas flowing into the catalytic converter. Although it is activated early, the temperature of the catalyst does not rise so much even in this case, so exhaust purification immediately after the engine is started will not reach a perfect level.

[0006]

If the temperature of the catalyst is low and the exhaust gas does not sufficiently react with the exhaust gas, the exhaust gas passes through the catalytic converter and is discharged to the atmosphere as it is. Therefore, warm-up operation is performed for a sufficiently long time. The present invention has been made in view of this point, and an object of the present invention is to provide an exhaust gas purification apparatus for an engine that can raise the temperature of the catalyst in a short time without requiring a long time for warming up the engine. It is a thing.

[0007]

As a means for solving the above problems, the present invention provides an exhaust gas purifying apparatus in which a catalytic converter is connected in the middle of an exhaust system passage connected to a combustion chamber of an engine. A flow path switching valve is provided in the subsequent stage, one outlet of this flow path switching valve is connected to the muffler, and the other outlet is connected to the inlet of the compressor. connection,
The outlet of this cylinder is connected to the inlet of the catalytic converter via a control valve.

In the above structure, the catalytic converter connected in the middle of the exhaust system passage connected to the combustion chamber of the engine is divided into the first catalytic converter and the second catalytic converter, and the flow path switching valve is divided into the first and second catalytic converters. The second catalytic converter is provided at the latter stage, and the outlet of the cylinder connected via the control valve is connected to the inlet side of the second catalytic converter.

Further, in the above apparatus, an oxygen concentration sensor is attached in the middle of the exhaust system passage.

Further, there are two oxygen concentration sensors, a first oxygen concentration sensor and a second oxygen concentration sensor, installed in the middle of the exhaust system passage, and the first oxygen concentration sensor is the first catalytic converter in the exhaust system passage. Of the second catalytic converter and the second oxygen concentration sensor is mounted on the downstream side of the second catalytic converter.

Then, the system path from the outlet of the cylinder storing the exhaust gas to the inlet of the second catalytic converter is made into two systems communicating with the upper part and the lower part of the cylinder, and a control valve is connected to each of these two systems. It is a thing.

Further, a temperature sensor for detecting the temperatures of the engine and the catalytic converter is provided, and an electronic control unit that operates by the output signal of the temperature sensor is provided. The flow control valve and the two flow control valves are provided by the output signal of the electronic control unit. It is configured to control the control valve.

[0013]

With this structure, when the temperature of the exhaust gas is not sufficiently raised immediately after the engine is started, the exhaust gas is not released into the atmosphere but is stored in the cylinder and fed back to the catalytic converter as needed. It is possible to raise the temperature in a short time. As a result, when the temperature of the catalyst rises, the flow path switching valve can be switched so that the exhaust gas is released into the atmosphere.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. 1 is an engine, 2 is a piston, 3 is a connecting rod, and 4 is a crankshaft. An intake passage 6 and an exhaust passage 7 are connected to the combustion chamber 5 located above the piston 2, and the intake passage 6 and the exhaust passage 7 are connected to each other.
An intake valve 8 and an exhaust valve 9 are provided. The exhaust passage 7 extends from a portion connected to the combustion chamber 5 to the muffler 10 and forms an exhaust system passage. A tail pipe 11 is connected to the tip of the muffler 10.

A first catalytic converter 12 is provided in the exhaust passage 7.
And a second catalytic converter 13 having a larger volume than this is connected in series. This connecting portion is branched, and the path 14 is connected to this branch, which will be described later.
Further, the connection point between the second catalytic converter 13 and the muffler 10 is branched to the system passage 16 via the flow passage switching valve 15, which will be described below. A temperature sensor is attached to the engine 1 and the first and second catalytic converters 12 and 13, and an output signal is input to an electronic control unit 38 described later.

A cooling device 17 is provided midway in the system path 16, and the tip thereof is connected to an inlet 19 of a compressor 18. 20 is an exit. The cooling device 17 may be of any type, but the simplest one is one in which a large number of fins as shown are attached to the outer periphery of the system passage 16. The compressor 18 includes an intake valve 21 at the inlet 19 and an outlet 20 at the outlet 20.
Is provided with a discharge valve 22, and in the portion of the compression chamber 24 formed in the upper part of the piston 23, the exhaust gas flowing from the system passage 16 is compressed by the piston 23 and discharged to the outlet portion 20. . The piston 23 is connected to the crankshaft 26 via a connecting rod 25. Crankshaft
26 is connected to the output shaft 28 of the motor 27.

Reference numeral 29 is a cylinder. This cylinder 29 has one inlet section 30 and two outlet sections 31 and 32.
The line 30 is connected to the outlet 20 of the compressor 18 by a system path 34 provided with a cooling device 33 on the way. Thus, the exhaust gas compressed by the compressor 18 is cooled by the cooling device 33 and stored in the cylinder 29. Of the two outlets 31, 32 of the cylinder 29, the outlet 31 is located above the cylinder 29 and the outlet 32 is located below the cylinder 29. The outlet 31 has a tip with a first catalytic converter.
The base end of a system path 14 connected between 12 and the second catalytic converter 13 is connected.

A midway portion of the system passage 14 is branched, and a path having a diameter smaller than that of the system passage 14 is provided between the branch portion and the outlet 32 of the cylinder 29.
Connected at 35. As a result, the exhaust gas passing through the two system paths 14 and 35 is guided to the second catalytic converter 13. A control valve 36 is connected in the middle of the path 14, and a control valve 37 is connected in the middle of the path 35.
These control valves 36, 37 are controlled by an electronic control unit (ECU) 38 described below.

The electronic control unit 38 includes a power supply terminal 39 and a ground terminal.
40 is provided, and a battery 41 as a power source is connected between the power supply terminal 39 and the ground circuit to which the ground terminal 40 is connected. The electronic control unit 38 is provided with two input terminals 42 and 43 and four output terminals 44 to 47 in addition to the input terminal (not shown) connected to the temperature sensor described above. The input terminal 42 is connected to a first oxygen concentration sensor 48 attached to the exhaust system passage 7 on the upstream side of the first catalytic converter 12. A second oxygen concentration sensor 49, which is also attached to the exhaust system path 7 on the downstream side of the second catalytic converter 13, is connected to the other input terminal 43.

Of the four output terminals 44 to 47, the output terminal 44
The flow path switching valve 15 is connected to the
Are connected. Further, control valves 36 and 37 are connected to the output terminals 46 and 47 as shown in the figure. Flow path switching valve 15
Switches the direction of the downstream side of the second catalytic converter 13 according to the output signal of the electronic control unit 38, the motor 28 operates to rotate and stop, and the control valves 36 and 37 connect and disconnect the system paths 14 and 35. Switch.

The exhaust emission control system of this engine constructed as described above operates as follows. First, when the engine 1 is started and then the warm-up state of the engine 1 and the first and second catalytic converters 12 and 13 is detected by the temperature detected by a temperature sensor (not shown), the electronic control unit 38
Determines the open state of the flow path switching valve 15 and the selection of use of the oxygen concentration sensors 48, 49. For example, engine 1 and second
If the temperature of the catalytic converter 13 is equal to or lower than the set value, the exhaust from the second catalytic converter 13 is made to flow toward the system path 16 in the opening direction of the flow path switching valve 15, and the exhaust is compressed.
Try to lead to 18.

At this time, the electronic control unit 38 sends an output signal to the motor 27 to operate the motor 27 and drive the compressor 18. When the compressor 18 is driven, after the engine 1 is started, the exhaust gas guided to the compressor 18 from the system path 16 is compressed, guided to the cylinder 29 from the system path 34, and temporarily stored therein. At this time, the control valve 3637 is closed. The cooling device 17 of the system path 16 and the cooling device 33 of the system path 34 are
It lowers the temperature of the flowing exhaust gas and increases the compression efficiency of the compressor 18 and the storage efficiency of the cylinder 29.

After the engine 1 is started, the temperatures of the engine 1 and the first and second catalytic converters 12 and 13 rise with the lapse of time.
When it is transmitted to the electronic control unit 38 by the output signal of 49,
The electronic control unit 38 compares the value with a set value, and when it exceeds the set value, the flow path switching valve 15 is switched so that the exhaust gas from the second catalytic converter 13 flows to the muffler 10 side. At the same time, the electronic control unit 38 switches the control valves 36 and 37 to eject the compressed exhaust gas stored in the cylinder 29 to the upstream side of the second catalytic converter 13.

The ejected exhaust gas is properly purified by the second catalytic converter 13 which is sufficiently activated by the temperature rise. The control valves 36, 37 are feedback-controlled mainly by an oxygen concentration sensor 49 provided downstream of the second catalytic converter 13.

When operating in this way, the catalytic converter is divided into the first and second catalytic converters 12 and 13, so that the exhaust gas stored in the cylinder 29 is injected to the second catalytic converter 13 in the subsequent stage. As a result, the first catalytic converter 12 that purifies only the exhaust gas from the engine 1 is not affected at all, and good purification can be performed. By mounting the oxygen concentration sensors 48, 49 in the middle of the exhaust system path 7, the electronic control unit 38 can be controlled according to the detection signals of the oxygen concentration sensors 48, 49.

Since this oxygen concentration sensor is composed of two sensors, a first oxygen concentration sensor 48 and a second oxygen concentration sensor 49, which are installed at different locations, the oxygen concentration at each site can be detected. Then, it will be possible to perform finer control.

Second from the outlet of the cylinder 29 for storing exhaust gas
The system path leading to the inlet of the catalytic converter 13 is connected to the upper side of the cylinder 29, and the system path connected to the lower side of the cylinder 29.
Since there are two systems of 35, the gas phase part of the exhaust gas inside the cylinder 29 passes through the system line 14, and the liquid phase part of the exhaust gas inside the cylinder 29 passes through the system line 14.
It will enter the second catalytic converter 13 through 35.
By separating the liquid phase and the gas phase, it is possible to use the dedicated valves for gas and liquid for the control valves 36 and 37 connected in the middle of the system paths 14 and 35, and to switch them efficiently.

A temperature sensor for detecting the temperatures of the engine and the catalytic converter is provided, and an electronic control unit 38 which operates by the output signal of the temperature sensor is provided.
Since the flow path switching valve 15 and the two control valves 36 and 37 are controlled by the output signal of the electronic control unit 38, the electronic control unit 38 always controls the flow path switching valve 15 and the two control valves 36 in relation to the temperature. , 37 will be able to control.

[0029]

Since the present invention is the engine exhaust gas purification apparatus configured as described above, during the engine cold start, the exhaust gas during warm-up is provided until the catalytic converter becomes active. Since it is not released into the atmosphere, it can be emitted at a low exhaust level. Then, since the exhaust gas stored in the cylinder is injected toward the second catalytic converter,
Even if it does not take a long time to warm up the engine, the temperature of the catalyst can be raised in a short time.

[Brief description of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention.

[Explanation of symbols]

 1 Engine 5 Combustion Chamber 7 Exhaust System Path 10 Muffler 12 First Catalytic Converter 13 Second Catalytic Converter 14 System Path 15 Flow Path Switching Valve 16 Path 18 Compressor 27 Motor 29 Cylinder 30 Inlet 31 Outlet 32 Outlet 35 Line 36 Control valve 37 Control valve 38 Electronic control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F01N 3/24 ZAB F

Claims (6)

[Claims] 1. In an exhaust gas purification device in which a catalytic converter is connected in the middle of an exhaust system passage connected to a combustion chamber of an engine, a flow path switching valve is provided at a stage subsequent to the catalytic converter,
One outlet of the flow path switching valve is connected to the muffler, the other outlet is connected to the inlet of the compressor, the outlet of the compressor is connected to the inlet of a cylinder for storing exhaust gas, and the outlet of the cylinder is controlled. An engine exhaust gas purification device, characterized in that it is connected to the inlet side of the catalytic converter via a valve. 2. A catalytic converter connected in the middle of an exhaust system passage connected to a combustion chamber of an engine is divided into a first catalytic converter and a second catalytic converter, and a flow path switching valve is a second catalytic converter. The exhaust gas purifying apparatus for an engine according to claim 1, wherein an outlet of a cylinder, which is provided at a subsequent stage and is connected via a control valve, is connected to an inlet side of the second catalytic converter. 3. The exhaust gas purification device for an engine according to claim 1, wherein an oxygen concentration sensor is attached midway in the exhaust system passage. 4. An oxygen concentration sensor installed in the middle of the exhaust system passage is provided as a first oxygen concentration sensor and a second oxygen concentration sensor.
The first oxygen concentration sensor is attached to the upstream side of the first catalytic converter in the exhaust system passage, and the second oxygen concentration sensor is attached to the downstream side of the second catalytic converter. The exhaust emission control device for an engine according to any one of 1 to 3. 5. A second outlet from an outlet of a cylinder for storing exhaust gas.
5. The system path leading to the inlet of the catalytic converter is formed into two systems communicating with the upper and lower parts of the cylinder, and a control valve is connected to each of these two systems. Engine exhaust purification device. 6. A temperature sensor for detecting the temperatures of an engine and a catalytic converter is provided, and an electronic control device that operates by an output signal of the temperature sensor is provided. The flow control valve and two flow control valves are provided by the output signal of the electronic control device. The exhaust gas purification device for an engine according to any one of claims 1 to 5, which is configured to control a control valve.